APSY 2216 Lecture 7: Feb 8_Research Methods and Analyses_Thomson

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Counseling, Developmental, and Educational Psychology
APSY 2216

ANNOUNCEMENTS ● Research Plan Drafts are due Friday on Canvas ○ First of two times you’ll turn in this assignment - just a draft ● You can sign up for Wednesday office hours on Canvas or just drop by ● Exam in two weeks: Wednesday, February 22 ● So far we have… ○ Identified a research problem ○ Defined a question and hypothesis ○ Reviewed the literature to find out what is known about the problem ● We still need to… ○ Determine the best method for studying what is not known ■ Sample participants - Who? ■ Instruments - What? ■ Procedure - When? Where? How? ■ Consider validity and reliability ○ Analyze and interpret data obtained through the method SAMPLING ● Sample - any group on which information is obtained ○ Should be representative of the population based on key characteristics (ex: gender, ethnicity, etc.) ○ Sampling - the process of selecting a number of individuals from a population, preferably in a way such that the individuals are representative of the larger group from which they were selected ○ Non-random sampling - not every member of the entire population has an equal chance of being selected → can be biased ■ Systematic sampling - obtained by selecting every nth name in the population ● Disadvantage: people may be arranged on a list in a particular order, if the whole population is available anyway, why not conduct random sampling? ● Least often done ■ Purposive sampling - selected based on personal judgment of the population, choosing based on specific characteristics that you would not know about the larger population ● Ex: selecting 100 students from each group: high GPA, middle GPA, low GPA ● Used pretty often ■ Convenience sampling - obtained based on availability of potential participants ● Ex: putting up posters in coffee shops ● Least ideal ● Theoretically, it produces a non-representative sample and should be avoided, but practically, one of the most commonly used sampling methods ○ Random sampling - method of selecting subjects from population by chance so that bias is less likely ■ Simple random sampling - take a list of every single person in your population and give them each an ID number, then use a random number table to pick subjects ● Advantages: if the random sample is large enough, it is likely to be representative of a population ● Disadvantages: technical difficulty (you need a list of every member of the population - impossible with a large population), subject to error, especially for smaller samples, no guarantee that all subgroups of interest are going to be adequately represented ■ Stratified random sampling - certain subgroups (strata) are preselected to reflect their proportion in the population → first divide population into strata (ex: SES and gender), then select a random sample from each stratum to preserve the proportion as it exists in the whole population ● Ex: 30% of population are high SES boys → select 30% of high SES boys for sample ● Advantages: increases likelihood of representation, ensures that key characteristics are included ● Disadvantages: only makes sense if we suspect that different strata may vary in their behaviors, technical difficulty (still need list of every member of population) ■ Cluster random sampling - random selection of groups instead of individuals → the more groups selected, the more likely the sample is to be representative ● Ex: select certain schools, certain classes, etc. ● Disadvantage: selected groups may not be representative ■ Two stage random sampling - first cluster sample, then simple random sampling ● Ex: randomly select zip codes (clusters) and then randomly select people within the zip code
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